1. Field of the Invention
The present invention relates in general to a marine engine, and more particularly to the layout of engine components of an outboard motor engine.
2. Description of Related Art
To improve the performance of a watercraft, the associated weight of and drag on the watercraft must be reduced. In regard to a watercraft's outboard motor, this means reducing the motor's weight and streamlining those portions of the motor which extend above or below the transom of the watercraft (i.e., the power head and the lower unit of the motor).
In connection with the motor power head, prior engine designs generally have not minimized the girth of the engine, and, thus, the size and weight of the protective cowling which surrounds the engine have not been minimized. Because the power head of a conventional outboard motor commonly extends well above the transom of the watercraft, a larger sized cowling produces more drag on the watercraft. A heavier cowling, of course, contributes to a greater overall weight of the watercraft which the motor must propel through the water. Both of these effects affect the performance of the watercraft.
In addition, an increased size and weight of the cowling makes it more difficult to remove the cowling, which is typically lifted over the engine. Increased size makes the cowling more cumbersome, and increased weight requires more strength to lift the cowling.
Although the desire to minimize the weight and size of the protective cowling is known, several engine components require specific spacing from one another. Conventional engine designs thus have increased the overall girth of the engine in order to accommodate such spacing requirements, and thus have increased the size and weight of the cowling.
For instance, the design of conventional cam covers accommodate the necessary spacing requirement between the cylinder head and a lubricant/ventilation gas separator, which is commonly located within a cam chamber of the cylinder head. In addition, conventional cam covers include an oil fill neck on the side of the cam cover. Japanese Patent Publication No. 3-32998 discloses an example of a conventional cam cover design. With the separator located on an inner side of the cam cover within the cam chamber, and with the oil fill neck located on the side of the cam cover, the height or profile of the cam cover (i.e., the extent to which the cam cover extends beyond the cylinder head) necessarily becomes greater. The overall girth of the engine thus increases.
Another example of prior engine designs increasing engine girth to accommodate spacing requirement between engine components involves the fuel supply system. The fuel pump and fuel filter of the fuel supply system conventionally are arranged on the intake side of the engine. The fuel filter is positioned in a lower tray of the cowling beneath the carburetors and the fuel pump is located on the side of cylinder head. Japanese Patent Publication No. 3-119562 discloses an example of this fuel supply system arrangement. Other conventional layouts position the fuel filter on the side of the cylinder head and the fuel pump on the cam cover.
These designs, however, require a larger cowling in order to distance the fuel filter from the cylinder head and block. The placement of the fuel filter adjacent the highly heated cylinder head commonly heats the filter to a sufficient temperature to vaporize the fuel within the filter. This creates a vapor lock and the engine stalls. To resolve this problem, conventional engine designs have increased the size of the cowling to distance the fuel filter from the cylinder head.
The conventional placement of the fuel filter in the lower tray beneath the carburetors also frustrates access to the filter. The filter typically can not be cleaned or changed without removing the entire filter housing. The position of the housing in the tight space between the lower tray and carburetors also makes removal difficult. To improve access to and to ease removal of the fuel filter, some prior designs have increased the size of the cowling; however, this results in the above-noted disadvantages of increased weight and drag.
In prior engine designs, the fuel pump commonly is located at the bottom of the cylinder head or cam cover in order for all fuel delivery conduits to extend vertically upward to the carburetors. Japanese Patent Publication No. 3-119562 discloses an example of this conventional fuel pump location. This arrangement, however, results in a substantial imbalance in the fuel travel distances between the carburetors, and complicates the even distribution of fuel between the carburetors.